This invention relates to a welding method in an automatic welding machine and, more particularly, to a welding method well-suited for use in selecting the welding conditions for an automatic welding machine, the motion of which is controlled by a robot.
Welding machines are available in which welding is performed by impressing a voltage across a wire and a workpiece to produce an arc at the tip of the wire, where the wire tip is moving along a welding path while the wire is successively laid out in small increments. FIG. 1 is a simplified view of such a welding machine, in which a wire WR is laid out in small increments in the direction of the arrows from feed rollers FR to protrude from the end of a torch TC via guide member GB. The amount by which the wire WR is fed is controlled in such a manner that the tip of the wire is situated at a position spaced a predetermined distance (e.g., 15 mm) from the surface of the workpiece WK. The plus side of a welding power supply PS for generating an intermittent high voltage having a predetermined period is applied to the wire WR through the guide member GB, and the minus side of the high-voltage power supply is applied to the workpiece WK. Gas from a gas supply unit (gas bombe), which is not shown, is supplied through the interior or the torch TC in the direction of the arrows so as to impinge upon the portion of the workpiece being welded to prevent the oxidation thereof. When a high voltage is generated intermittently by the welding power supply PS while the gas is fed from the gas supply unit and the wire is laid out in small increments, an arc is produced at the tip of the wire and both the wire and the portion being welded are melted to weld the fused portions together.
In a welding machine of this type, welding conditions such as optimum welding voltage, wire feed speed, preflow duration, postflow duration and crater processing duration are decided in dependence upon the wire material and the material of the workpiece portion being welded, welding speed and the like. Accordingly, when conventionally welding, the optimum welding conditions are set on dials or the like and welding is performed based on the set welding conditions. However, since the welding voltage, wire delivery speed, preflow duration, postflow duration and crater processing duration must be set using the dials or the like, drawbacks are encoutered in that setting of the welding conditions is complicated and changing welding conditions cannot be performed in a simple manner. Furthermore, in a case where the welding conditions differ at the start and at the completion of welding, the welding conditions must be set on the dials for each occasion, thereby rendering the operation of setting the welding conditions even more troublesome. Moreover, a large number of dials are required, thereby raising the cost of the welding machine.